Improving the effectiveness of CO2 as a refrigerant
Summary of technology
Carbon dioxide has been used in the past as a readily available, low cost, non-toxic and non-flammable refrigerant. However, CO2’s intrinsic properties, such as its relatively high triple point of -56.6°C, limits its ability to cool to low temperatures. As a result, synthetic CFC refrigerants have superseded CO2 as industry’s preferred refrigerant.
Curtin University has recently conducted experiments that show the addition of a small amount of a specific, light hydrocarbon agent to CO2 can successfully lower CO2’s triple point to -78.5°C at atmospheric pressure. This changes the phase diagram of CO2 so it can be used as a refrigerant at lower temperatures and pressures.
Lowering CO2’s triple point makes it a useful addition to the list of currently available industrial refrigerants, alongside ethane, which has a boiling point of -89 °C and propylene, which has a boiling point of -47.6 °C. CO2’s inert nature is also an advantage, particularly in offshore processing plants where risk factors are high.
Further applications include:
- as a refrigerant in cascade refrigeration for producing liquefied natural gas as a safe refrigerant to achieve a temperature of -78.5 °C
- as an industrial and commercial refrigerant.
Associate Professor Dr Ahmed Barifcani at Curtin University’s School of Chemical and Petroleum Engineering.
Stage of development
Tests have successfully lowered CO2’s freezing point to -78.5 °C and have verified the new phase diagram.
Intellectual property is owned by Curtin University. A provisional patent has been filed.
We are looking for a partner to collaborate on the next stage of development, which is likely to be a bench scale demonstrator.